1. The Field of the Invention
This invention relates to knot-tying devices and, more particularly, to a novel mechanical knot device and methods which may be used to securely fasten objects together and which is capable of being quickly and safely released from the body of a rope or tethering material experiencing tension or load strain.
2. The Background Art
Throughout history, the ability to secure one article to another has been a valuable and extremely important skill. One of the earliest known methods for securely fastening objects together involved the use and manipulation of plant vines. For example, huts were traditionally constructed by interweaving freshly cut vines around branches and tree limbs of various lengths and thicknesses. Securing the branches and limbs together, the vines provided a means for restricting any subsequent movement of the branches and limbs in relation to the overall structure of the shelter or hut. Furthermore, plant vines provided necessary structural support to the integrity of the hut once the vines dried in their prearranged configurations.
Today, ropes are customarily used when fastening one object securely to another. Typically, ropes are made from either natural or synthetic fibers. When a load or stress is first applied to any fiber rope, the rope stretches in a proportional degree to the magnitude of the load applied. Normally, the load stretch is referred to as the strain on a rope. The strength and integrity of a rope to withstand a load strain generally depends upon the size of the rope, the properties and characteristics of the fiber strands of the rope, and the technique by which the fiber strands are braided or interlaced together to form the rope.
Traditionally, a rope formed from natural fibers is typically produced from such plants as manila, sisal and hemp. A rope constructed from synthetic fibers, on the other hand, is generally formed from elastic synthetic materials or polymers, such as nylon and polypropylene.
Synthetic ropes are typically stronger than natural fiber ropes, with nylon being about 21/2 times the strength of manila. In addition, synthetic ropes are generally lighter and have greater tolerances for fatigue and resistance to fiber abrasions. Synthetic ropes also have a higher breaking strength (wet or dry), greater elasticity and tensile recovery, superior absorption abilities under impact and shock loads, greater flexibility, and are ultimately better able to resist rotting than ropes fabricated from natural fibers.
Since ropes are being increasingly utilized for numerous recreational and occupational purposes, such as, for example, yachting, construction rigging, ranching and mountain climbing, a number of knot-tying configurations have been developed to demonstrate strength and holding integrity. When forming a knot configuration in a rope, the principal objectives include providing security against slippage, suitability of the particular knot configuration to the circumstances and strength or holding integrity of the rope. In this regard, the proper fastening means (a knot, bend or hitch) must be carefully selected for the particular task and then tied correctly to obtain the maximum holding strength needed from the knot formed in the rope. Accordingly, conventional knot-tying has become essential, if not invaluable to the effective performance of a rope when securing objects together.
Several inherent problems, however, are associated with the use of conventional knots. For instance, many of the knots recognized as providing the greatest load carrying capacities generally require the user to possess an expertise in knot-tying and an ability to distinctly remember from the hundreds of various knot configurations which knot works best under which particular set of circumstances.
In some situations, the similarities between the various knot-tying forms and configurations may cause a user frustration when carefully deliberating the specific steps to follow when tying the appropriate conventional knot to provide the necessary holding integrity as required by the inherent factors of the particular conditions. Various types of conventional knots requiring specific tying configurations include, for example, the bowline knot, the double blackwall hitch, the catspaw, the clove hitch, the half-hitch, the square knot, the sheepshank, the rolling hitch, the timber hitch and the overhead knot.
Another important property of a rope is its ability to endure dramatic bending under load conditions. Repeated bending of a rope is commonly referred to as flexing endurance and its effect on the performance and strength of the rope is an important factor concerning load carrying capacity.
It has been well documented by those skilled in the art that tying a knot in a rope or severely bending the rope may cause a significant reduction in the strength and load carrying capacity of the rope. This reduction in load carrying capacity is directly proportional to the tightness of the knot or the sharpness of the bends in the rope. Severe bends or knots tied in the body of a rope, therefore, may significantly interfere with the stress distribution of the fibers which make up the integral strands of the rope.
Typically, a rope fastening means (knot, bend or hitch) formed in the body of a rope is normally unable to display the same relative strength and load carrying capacity of the original rope without bends or knots formed therein. Moreover, the bending of a rope when forming a knot or hitch may cause the outside fibers to carry more than their share of the load strain acting on the rope. Accordingly, the resultant stretching of the fibers may permanently weaken the holding integrity of the rope. In this regard, when a failure occurs, the outside fibers are the first to break, followed by the inside fibers.
Regarding the load carrying capacity of a rope, with a straight pull, a rope will give 100% efficiency. Tie a knot in the same rope or bend it severely and the load carrying capacity of the rope is significantly weakened approximately 50%. For example, a bowline knot and a square knot formed in the body of a rope can dramatically reduce the strength and load carrying capacity of the rope by 40% and 50%, respectively. A sharp bend in a rope may also result in a 25% reduction in rope strength. Tying a knot or severely bending a rope, therefore, has multiple disadvantages which may significantly reduce the overall effectiveness of the rope. Consequently, the formation of a conventional knot in a rope may cause serious fatigue to the fibers of the rope, thereby shortening the usefulness and life expectancy of the rope.
Another practical disadvantage with using conventional knots relates to the problems associated with exposing a rope to excessive amounts of pulling forces or tension which may cause a knot formed in the body of the rope to become severely constricted and compressed, thus making it nearly impossible to untie the knot without cutting the rope. When this occurs, the knot generally becomes permanently fixed within the body of the rope, until such time as the rope is cut and the conventional knot configuration removed. Consequently, having to cut the rope to release the holding integrity of the knot, may result in significant rope waste.
A number of attempts have been made by those skilled in the art to overcome many of the foregoing disadvantages associated with tying conventional knots. For example, to help alleviate the prerequisite that a user manifest a degree of technical expertise and specialized know-how to tie a knot with holding integrity, prior art mechanical knot-tying guides were developed. Knot-tying guides typically provide a set of tying instructions printed directly on the exterior surface of the guide device to assist the user in forming a particular conventional knot.
Although the use of knot-tying guides has provided users with an effective resource when tying certain conventional knots, mechanical knot-tying devices of the prior art typically require the user to acquire a certain amount of practice or experience with the device before the knot-tying guide is generally helpful. In addition, mechanical knot-tying guides are normally limited in their use to a very specific knot configuration. For example, knot-tying guides were developed by those skilled in the art to assist users in forming conventional necktie knots, such as the windsor or four-in-hand knot. These prior art knot-tying guides are, however, strictly limited in fundamental application to tying a specific knot configuration for a necktie.
As another example, because the bowline knot is known for its holding integrity and usefulness, prior art mechanical knot-tying guides were developed to assist a user in properly tying a bowline knot without requiring the user to possess the technical know-how and expertise generally required for tying a bowline knot. Notwithstanding the usefulness of bowline guide devices, in order for the knot-tying guide to be beneficial, the user is typically required to carry the bulky and cumbersome device to those locations where objects are to be secured to one another.
Other practical disadvantages with bowline knot-tying guides have also emerged, such as the difficulty for a user to maintain control over a moving object while having to dedicate almost entire concentration to the instructional placement of the rope into the various grooves provided by the device to properly construct an adequate bowline knot that demonstrates sufficient holding integrity. Despite the effectiveness of knot-tying guides offered by the prior art, the influence and effect of a bowline knot on a rope traditionally reduces the strength and load carrying capacity of the rope by nearly 40%. And, since bowline knots are often preferred over other conventional knots when tethering large objects, significant problems may arise if the properties of the rope, such as its fiber strength and load carrying capacity, are not seriously taken into consideration by the user.
When tying a string or rope around a box or package, it is often difficult, if not impossible, for one person to tie the knot alone. Accordingly, those skilled in the art developed various mechanical knot-tying contrivances to eliminate the need for assistance from another person to tie a knot displaying holding integrity. Unfortunately, the prior art knot-tying contrivances are generally bulky in size and typically not very portable. Moreover, a conventional knot formed in the rope or cordage with these knot-tying contrivances usually becomes a permanent fixture within the body of the rope or cordage. In order to remove the knot, the cordage is typically cut and the knot retied.
Other prior art mechanical knot-tying devices were also developed to offer improvements to the methods used by fisherman when releasing fish from fish stringers. One such prior art device involves the method of tightly wedging a string or cord between a rigid circular loop which is formed in the center of an elongated wire and underneath a portion of the overlaying string.
By removing the wedged portion of the string from its position, the fish stringer device allows the fisherman to dislodge the fish from the device without having to rethread the string through the fish. The fish are unable, however, to be dislodged from the fishing line if even a moderate amount of tension is acting against the body of the string. Accordingly, the string wedged between the two surfaces may become further wedged therebetween presenting a potential problem regarding serious fiber abrasions and fatigue to the string, thus weakening the load carrying capacity and strength of the string, especially in the area where the string or rope is tightly wedged.
Consisting of a core of stranded metal fibers with a plastic protective coating, metal cables were later developed to provide greater durability and resistance from the weather as compared to conventional cordage. Pull cords, tennis net supports and clothes lines are a few examples of plastic coated metal cables of the prior art. A disadvantage, however, to using metal cables as a securing means is the general difficulty of effectively assembling two lengths of cable together to form a loop in the body of a cable for passing around an object to be fastened thereto. In this regard, tying a conventional knot in a cable has proven to be generally ineffective when it comes to providing load carrying capability due to the distinct properties and characteristics of a cable, such as thickness, a smooth surface and its relatively unyielding flexibility. In addition, a conventional knot formed in the body of a metal cable is typically unable to withstand high tension forces applied against the cable without the knot configuration unraveling and releasing.
Responding to the general inability of tying conventional knots in cables and the difficulty associated with securing cable assemblies together, prior art devices were developed providing alternative mechanical means for substantiating holding integrity between cables. For example, metal clamps were provided which were tightly fastened to the body of a cable by puncturing through the plastic coating of the metal cable and contacting the metal fibers. In this fashion, prior art metal clamps provide a form of resistance from slippage between multiple cables. The disadvantage, however, with cutting or puncturing a metal cable is that its fibers may become weakened and fatigued from the exposure to the elements of the weather, whereby permitting a form of damaging rust to generate on the metal fibers of the cable significantly affecting the overall strength and life of the cable. As an alternative to prior art metal clamps, mechanical knot devices comprising at least two figure-eight shaped metal rods that interact in association with one another and the body of at least one cable were developed to provide a solution to the damage caused by metal clamps to cable fibers. By interlacing the body of the metal cable through various openings in each of the figure-eight shaped rods, a knot assembly with holding integrity may generally be formed.
Although prior art metal rods are typically useful when manipulating plastic coated metal cables, the cost of producing is significantly double the cost of manufacturing a single mechanical knot due to the need of at least two figure-eight metal rods interacting together in combination with the cable to provide holding integrity. In addition, the mere act of interweaving the cable through the various openings in figure-eight shaped rods may further restrict the capacity of the cable to be quickly and safely released from the metal rods under any form of tension or load strain. Accordingly, any tension acting against the cable must be fully relaxed or the section of the cable interacting with the metal rods must be cut to release the restrictive hold of the mechanical knot device and knot configuration formed thereby.
Alleviating the dangers and drawbacks associated with alternating tensions and rope slackening caused by variations in load pressures typically having detrimental effects on the fastening ability of common hooking devices and spliced-end loops, another form of mechanical knot devices was developed consisting generally of a tubular support body through which the body of a rope may be inserted therethrough and tied into a restrictive knot configuration therearound. After passing the first end of the rope around a fixed or moveable object, the rope is typically tightly wrapped around the small diameter of the mechanical knot device at least two times and secured each time under the portion of the rope inserted through a slot formed in the elongated body of the tubular support. Once a knot configuration is formed around the tubular mechanical knot-tying device and an amount of tension or load strain is applied against the rope, the knot device positioned in the body of the rope generally becomes permanently fixed in the rope until the tension or strain acting on the rope is released, or the mechanical knot device is excised from the body of the rope.
Another significant disadvantage with tubular knot devices of the prior art is that the formation of the knot configuration requires sharp bends in the body of the rope to form a secure hold. Tightly wrapping the rope around the small tubular radius of the mechanical device is also likely to cause stress and fatigue to rope fibers and significantly reduce the overall strength and load carrying capacity of the rope. Furthermore, since one end of the rope is typically pushed through a milled slot formed in the body of the tubular member to provide a catchment for the knot configuration, the danger that a user's fingers might become caught in the opening of the slot when tension is suddenly applied against the body of the rope is clearly a serious concern for users of these prior art tubular mechanical knot devices.